AC (Alternating Current) Electrical current that alternates direction (positive
to negative). AC is often contrasted with direct current (DC), commonly produced by
batteries.

Absorption The tendency of sound waves to be soaked up by soft surfaces.
Opposite: reflection.

Acoustic FeedbackFeedback, the dreaded
"sound man's (and sound woman's)curse," is caused by a regeneration of sound
leaving a speaker and entering a microphone. This tone - a sustained shriek - is a
self-perpetuating cycle which can be stopped by decreasing the volume. Sometimes referred
to as a standing wave.

Acoustics 1. The science or scientific study of sound. 2. The properties of a
room or environment that affect the qualities of sound.

Acoustic Power Output The output, as measured in watts, of anything that
generates sound.

Acoustic Suspension A type of speaker cabinet which is sealed to control the
action of its woofer and prevent the leakage of air.

Ambient Noise Level "Background" noise - from any source - that
affects the listener's ability to hear what is produced by a sound system. Machinery, hum
from florescent lights, traffic, et.

Amperes, Amperage (Amps) Units of electrical current.

Amplifier (Amp) 1. An electronic device that increases the amplitude of a
signal. 2. A combination speaker/ampflier designed for use with an instrument, as with a
guitar amp or keyboard amp. See preamp; power amplifier

Amplitude 1. The strength of sound waves or an electrical signal, as measured
against a mean. 2. That which determines loudness.

Anechoic 1. The complete absence of reflected sound (echo). 2. An environment
that prevents (through dissipation and absorption of sound waves) all reflected sound, as
in an anechoic chamber.

Attenuate To make weaker. An attenuator uses
resistance to reduce output voltage, as with a volume control.

Balanced Line A pair of ungrounded conductors whose voltages are opposite in
polarity but equal in magnitude. Balanced lines reduce interference from external sources
like radio frequencies and light dimmers since they are typically shielded by a third
conductor surrounding them.

Basket The frame to which a driver's cone is mounted.

Bass The lower end of the frequency range, from about 20 Hz to about 300 Hz.

Bass Reflex A speaker that, as a means of enhancing the efficiency of the
reproduction of bass frequencies, channels some of the sound pressure generated by its
woofer(s) through an opening (port) in its cabinet.

Biamplification The use of separate amplifiers to power woofers and tweeters.
See crossover

CPS (Cycles Per Second) The number of plus/minus voltage swings or
compressions/rarefactions of air molecules occurring each second in an electrical or audio
signal; usually expressed as hertz (Hz).

Cardioid "Heart" shaped pattern exhibited by some microphones which
reduces pick-up from the sides and back.

Clipping Audible distortion that occurs when a signal's level exceeds the limits
of a particular circuit. When an amp is "turned up too loud," and begins to
distort, it is said to be clipping. On an oscilloscope clipping appears to flatten the
tops and/or bottoms of the wave forms as if someone took a scissors and "clipped or
cut" the top and bottom of the wave.

Compression Driver A transducer, designed for use
with a horn, which utilizes a diaphragm (rather than a cone) to reproduce mid and high
frequencies. See: Horn

Condenser Microphone A mic that depends on an external power supply or battery
to electrostatically charge its condenser plates.

Conductor A substance - in electronics, usually a metal - that allows the free
flow of electrons.

Cone The vibrating diaphragm, employed in some speakers designs, that generates
sound waves.

Console A large or elaborate mixer required to massage the
ego of the band's sound man.

Critical Distance The distance from a sound source at which sound pressure
levels emitted by the source equal those being reflected off of other surfaces.

Crossover (Crossover Network)- Electronic An electronic
device or circuit that, when inserted between a mixer and amplifier, divides the audio
spectrum into individual frequency ranges (low, high, and/or mid) before sending them to
specialized amplifier/speaker combinations. An advantage of this type of crossover is that
it increases efficiency.

dB (Decibel) 1. A relative unit of measure between two sound or audio signal
levels. A difference 1 dB is considered to be the smallest that can be detected by the
human ear. An increase of 6 dB equals twice the sound pressure. 2. As a measure of sound
pressure levels, used to indicate loudness.

DC (Direct Current) Electrical current that flows in only one direction.

Delay 1. The postponement of an audio signal for a specific amount of time,
usually measured in milliseconds. 2. A device designed to delay an audio signal.

Diaphragm 1. The radiating surface of a compression driver; its vibrations emit
sound waves. 2. The moving element of a microphone.

Dimmer Noise (hash) The noise that originates in the switches used to dim lights
and can be heard in a sound system.

Directivity The ability of a speaker or horn to direct sound to a given area
which can be described by its directivity factor (Q).

Dispersion The area throughout which the sound produced by a speaker is
distributed.

Distortion Any discrepancy between the source material and the sonic output of a
sound system.

Ducking The use of an electronic device to automatically reduce the volume of
music or other background fill when an announcer begins speaking.

Dynamic Microphone A microphone that converts sound into electrical pulses by means of
a moving electromagnetic coil.

Dynamic Range The difference between the softest and loudest extremes within an
audio signal.

Dynamics Processing The use of electronic devices to control the levels of audio
signals and compress or expand their dynamic range.

FerroFluid An emulsion containing metal particles, used to conduct heat away
from a speaker's voice coil.

Filter A device that removes unwanted frequencies or noise from a signal.

Flat The state of an audio signal or tone whose frequency is unaltered by
equalization. On most mixers and equalizers flat is indicated by the tone controls being
at dead center.

Fletcher Munson Curve A graphic representation of average hearing responses of
carbon based units at particular sound pressure levels.

Foldback an output, that by splitting an input signal (independently of the
mixer controls), allows that signal to be sent a separate device. Foldback makes it
possible for a performer to create his/her own monitor mix without affecting the front of
house mix.

Frequency 1. The number of sound waves that pass a given point in one second. 2.
The determiner of pitch. (Ask Kenneth).

Frequency Response The range of frequencies that are reproducible by a speaker
or electronic component.

Front of House (FOH) the components of a PA that are directed toward the
audience, as opposed to the back of the house or monitor system.

Impedance The measure of total resistance to the current flow in an alternating
current circuit; expressed in ohms, as a characteristic of electrical devices
(particularly speakers and microphones). Most speakers are rated at 8 ohms. Microphones
are usually classified as being either high impedance (10,000 ohms or greater) or low
impedance (50 to 250 ohms).

Inductance A circuit's opposition to a change in current flow.

Input Overload Distortion Distortion caused by too great an input signal being
directed to an amplifier or preamplifier. Input overload distortion is not affected by
volume control settings and most frequently occurs when mics are positioned too close to
the sound source. Input overload distortion is controllable through the use of an
attenuator.

Inverse Square Law The law that states that in the absence of reflective
surfaces, sound pressure 9or light) falls off at a rate inverse to the square of the
distance from its source. In other words, every time you double your distance from the
sound source, the sound pressure level is reduced by 6 dB.

Microphone Processor A device that, when installed between a mic and an amp or
preamp, allows the manipulation of the signal originating at the mic.

Mixer An electronic device that permits the combining of a
number of inputs into one or more outputs. Mixers commonly provide a variety of controls -
tone, volume, balance and effects - for each "channel." See: Board, Console.

Monitor A speaker or earphone dedicated to making it possible for a performer to
hear - or monitor - his/her own performance. Examples are: floor wedges, sidefills, or
mini-monitor.

Patch Cord A short electrical cable used to connect individual components of a
sound system

Personal Monitor A monitor that is small enough to be directed at a specific
performer. Before these devices, monitors were usually arrayed along the front of the
stage and shared by the entire ensemble.

Piezo Tweeter A driver which is dedicated to the reproduction of high
frequencies and operated by means of a crystal rather than an electromagnet.

Phantom Power Operating voltage supplied to a condenser mic by a mixer or
external power source.

Phase The relationship of an audio signal or sound wave to a specific time
reference.

Phase shift The phase relationship of two signals at a given time, or the phase
change of a signal over an interval of time.

Pin 2 Hot Considered the standard polarity for pro audio.

Pitch Tone: A function of frequency.

Polarity A condition which has two states (in or out) and is usually described
in one of three ways: 1. Acoustical to electrical (microphone): Positive pressure at
diaphragm produces positive voltage at pin 2 of XLR or at the tip of a ¼-inch phone plug.
2. Electrical to acoustic: Positive voltage into the "plus" terminal of a
speaker causes the speaker's diaphragm to move forward (produces positive pressure). 3.
Electrical to electrical: Positive voltage into pin 2 of an XLR plug or at the tip of a
¼-inch phone plug produces positive voltage at the output (pin 2 of XLR jack, the tip of
a ¼-inch phone plug, or the red (plus) connector of a binding post (banana terminal)).

Potentiometer (Pot) A variable resistor (rotary or linear) used to control
volume, tone, or other functions of an electronic device.

Power AmplifierAn electronic device that increases
the volume of a signal. A basic unit of all sound systems. Power amps are typically
connected to a preamp which provides controls for individual functions: level, tone, etc.

Q A ratio obtained by complex mathematical calculations involving the
relationship of a speaker's direct radiated energy to its total radiated energy
(directivity index). When measured on-axis, Q (which is dependent on frequency) is used to
determine a speaker's suitability for a particular application.

SPL (Sound Pressure Level) A measurement of the volume of sound, expressed in
decibels (dB): a function of amplitude.

Sensitivity The sound pressure level directly in front of the speaker (on axis)
at a given distance and produced by a given amount of power.

Shield A metal enclosure that prevents electronic components from being affected
by unwanted interference. Shielded speakers may be placed near a TV, for instance, because
their magnets cannot affect the picture tube.

Shelving The setting of the on-axis output of complementary drivers (woofers,
mid-range, tweeters) to provide the desired frequency response.

Sibilance A hissing sound produced when pronouncing S and Z. Sibilance is
undesirable in professional sound reinforcement and can be controlled through the use of a
"de-esser" like Valley Audio's 401 Microphone Processor, 815 Dynamic Sibilance
Processor, or 730 DynaMap Digital Dynamics Processor.

Signal An electrical impulse. First popularized by Paul Revere.

Signal-To-Noise-Ratio The ratio, expressed in dB, of an electronic device's
nominal output to its noise floor.

Snake A cable - often runing between the stage and control board - that combines
multiple lines; used to connect mics, instruments and monitors to a mixer.

Sound Level Meter A device that measures, in dB, the amplitude of sound waves.

Sound Pressure Level (SPL) The measurement of loudness, or amplitude, of sound,
expressed in dB.

Sound Reinforcement The use of electronic devices to reinforce, alter or
increase the level of sound.

Spider An internal speaker component whose function is to precisely position the
voice coil in relation to a gap in the motor.

VCA (Voltage Controlled Amplifier) An amplifier whose output is controlled by
varying its voltage rather than by direct resistance (as with a potentiometer).

Voice Coil Wire, usually copper, wrapped around a former (tubular core). When
attached to a cone or diaphragm, surrounded by a magnetic field, and set into vibration by
an alternating current, a voice coil causes a speaker to emit sound waves.

Voltage The electrical pressure (electromotive force) of a current within a
circuit.